1. Technical Field
The present invention relates to a substrate for a sensor, a physical quantity detection sensor, an acceleration sensor, an electronic apparatus, and a moving object.
2. Related Art
In the related art, for example, as described in JP-A-2012-189480, a physical quantity detection sensor is known in which a physical quantity detection element for detecting a physical quantity is fixed to a substrate for a sensor (a cantilever section) having a base section (a fixed section), a movable section connected to the base section, and a support portion extending along the movable section from the base section when viewed in a planar view as viewed from a thickness direction of the movable section. In the physical quantity detection sensor, the physical quantity detection element is fixed, at one end thereof, to the base section and fixed, at the other end thereof, to the movable section. Further, the physical quantity detection sensor is provided with a mass section disposed on at least one of both principal surfaces of the movable section and disposed so as to partially overlap the support portion when viewed in the planar view.
In the physical quantity detection sensor having such a configuration, in a case where impact exceeding a design value is applied thereto, if the displacement of the movable section is increased beyond a design value, the movable section strongly comes into contact with an undesirable place, or stress is applied to a connection portion between the movable section and the base section, whereby there is a concern that the substrate for a sensor or the physical quantity detection element may be broken. In order to avoid this problem, the physical quantity detection sensor of JP-A-2012-189480 has a configuration in which a predetermined gap is provided between the mass section and the support portion at an area where the mass section and the support portion overlap, when viewed in a planar view as viewed from a thickness direction of the substrate for a sensor. In this way, when a physical quantity (for example, acceleration) in a thickness direction (a Z direction) is applied to the physical quantity detection sensor, the displacement of the movable section which is displaced according to acceleration can be restricted due to the mass section disposed on a principal surface of the movable section coming into contact with the support portion when the mass section has been displaced by an amount corresponding to the predetermined gap.
Further, in JP-A-2000-338124, there is introduced a physical quantity detection sensor (a semiconductor acceleration sensor) in which at a portion of the inner peripheral surface of a support portion extending along a movable section from a base section when viewed in a planar view as viewed from a thickness direction of the movable section, a protrusion portion (a stopper portion) which makes the distance between the inner peripheral surface of the support portion and the movable section (a weight section) smaller than at other sites is provided to protrude. Due to this configuration, when a physical quantity in a direction intersecting a thickness direction (an in-plane direction of the movable section and the support portion) is applied to the physical quantity detection sensor, the displacement of the movable section (the weight section) which is displaced according to the physical quantity is restricted by the protrusion portion provided to protrude on the inner peripheral surface of the support portion, whereby excessive displacement of the movable section (the weight section) is restricted, and thus it is possible to prevent breakage of a substrate for a sensor or a physical quantity detection element.
In the physical quantity detection sensors of JP-A-2012-189480 and JP-A-2000-338124 described above, substrate for a sensor having base section, movable section, and support portion is integrally formed by etching a single crystal material such as quartz crystal or silicon.
In a case of forming the outer shape of the substrate for a sensor of the physical quantity detection sensor by wet-etching quartz crystal among single crystal materials which are used as a material for forming the substrate for a sensor, it is known that because of etching anisotropy due to a difference in etching rate in the respective crystal axis directions of the quartz crystal, it is difficult to accurately form a gap in the in-plane direction of the movable section and the support portion at a desired length. However, in JP-A-2000-338124, a method or the like of accurately forming the gap between the movable section and the protrusion portion on the inner peripheral surface of the support portion is not described at all. For this reason, the gap between the movable section and the protrusion portion (a restricting portion or a stopper portion) becomes longer than a predetermined length, and thus, in a case where impact exceeding a design value is applied to the physical quantity detection sensor, there is a concern that the substrate for a sensor or the physical quantity detection element may be broken. Further, in a case where the gap between the movable section and the protrusion portion (the restricting portion) becomes shorter than an appropriate length, the displacement range of the movable section is restricted to be smaller than in the settings, and therefore, there is a concern that the set detection range of a physical quantity such as acceleration may not be able to be satisfied.